1. Preheat the oven to 180C/350F/gas mark 4. Butter a 2023cm cake tin and line the bottom with greaseproof paper. Pour 2 tbsp of the maple syrup on to the paper and arrange half of the apple slices in an attractive pattern on the base.
2. Cream the butter and the caster sugar with an electric whisk until light and creamy. Add half of the beaten egg and whisk until smooth.
3. Sift together the flour, cinnamon and baking powder. Add half of this mixture to the butter, sugar and egg and whisk quickly to incorporate. Then add the rest of the egg and the rest of the flour. Stir in the remaining maple syrup and apple slices.
3. Spoon the mixture into the tin and bake for 3540 minutes or until a skewer inserted in the middle comes out clean. Cool on a rack.
4. To serve, loosen the sides with a knife and carefully turn upside down on to a serving plate and peel off the paper. Serve with lightly whisked cream if desired.
Tip: To make this cake mixture into muffins, chop the apples into chunks and stir all of them into the cake batter. Sprinkle the top with brown sugar and cinnamon and bake in muffin tins.